PROCESS FOR THE PRODUCTION OF N-(TERT- AMINOALKYL)ACRYLAMIDES

METHODE D'OBTENTION DE N-(AMINOALCOYLE TERT.) ACRYLAMIDES

English Abstract

ABSTRACT
This invention describes a process for the production of N-(tert-amino-
alkyl)acrylamides by the reaction of acrylic acid with a suitable tertiary
aminoalkylamine at a temperature of 150-230° C. The aminoalkylamine and
acrylic acid are reacted in equimolar quantities, preferably in the presence of
an acidic or a basic catalyst.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for preparing an N-(tert-aminoalkyl)acrylamlde of the
general formula
<IMG> (I)
wherein R1, R2, R3 and R4 are in each instance a straight or branched chain C1
to C4-alkyl group, comprising reacting acrylic acid with a tertiary amino-
alkylamine of the general formula
<IMG> (II)
wherein R1, R2, R3 and R4 are as hereinbefore defined at about 120° C. to
300° C.
2. A process according to claim 19 wherein the reaction temperature is
from about 150° C. to 230° C.
3. A process according to claim 1, wherein the reagents are acrylic acid
and tertiary aminoalkylamine in equimolar quantities.
4. A process according to claim 1, wherein the reaction is performed in

the presence of catalytic quantities of acidic or basic substances.
5. A process according to claim 4, wherein said acidic or basic
substances are selected from organic and inorganic acids and bases, Lewis acids
and bases, and ion-exchange agents.
6. A process according to claim 1, 2 or 3, wherein the reaction is
performed in the presence of one or more polymerization inhibitors selected
from the group consisting of p-dioxybenzol, p-methoxyphenol, N-pnenyl-.beta.-
naphthylamine, phenotiazine, N,N-diphenyl-p-phenylenediamine, copper powder and
copper salts.
7. A process according to claim 1, 2 or 3, wherein the N-(tert-amino-
alkyl)acrylamide product is isolated from the reaction mixture by distillation.
8. A process according to claim 4 or 5, wherein the reaction is
performed in the presence of one or more polymerization inhibitors selected
from the group consisting of p-dioxybenzol, p-methoxyphenol, N-phenyl-.beta.-
naphthylamine, phenotiazine, N,N-diphenyl-p-phenylenediamine, copper powder and
copper salts.
9. A process according to claim 4 or 5, wherein the N-(tert-amino-
alkyl)acrylamide product is isolated from the reaction mixture by distillation.

Description

This invention describes a process for the production of N~(tert-amlno-
alkyl~acrylamides which are particularly valuable in homo- and copolymerization
processes, resulting in the manufacture of homo- and copolymers which are
useful as flocculating and dewatering agents and also as suspending agents and
dry and wet strength enhancers in paper-maklng.
A numher of processes for the production of N-(tert-aminoalkyl)acrylamides
may be found in the literature. For example, German DT-OS 25 02 247 teaches
that during the conversion of acrylic acids or acrylic esters, respectively,
with a double molar excess of N,N-dialkylalkylene diamines, the corresponding
~-aminopropionic acid amides result and that the N-(tert-aminoalkyl)acrylamides
can be produced from these by removal of the amino group from the ~-position.
However, the high pyrolysis temperatures required for this process promote the
formation of undesirable by-products as well as polymerization of the
acrylamides. Furthermore, the cleaning of the cracking products requires
costly distillation technology. Accordingly, this two-stage operation has
generally been considered unsatisfaceory.
In the process described in German DT-OS 28 09 102 and DT-OS 28 16 516,
the esters of the (meth)acrylic acid are converted to the N-substituted
(meth)acrylamides with a sub-stoichiometric amount or only a slight excess of
N,N-dialkylene diamine in the presence of dialkyl stannic oxide or iron ions,
respectively. In this process, however, the desired (meth)acrylamides are not
obtainable at satisfactory rates of yield. Furthermore, DT-OS 28 09 102
specifies that the operations must be carried out under pressure.
US patent 3,6529671 describes a process for the production of N~(dialkyl-
aminoalkyl)methacrylamides in which ~ethacrylic acid and N,N-dialkylalkylene
diamines in equimolar amounts are sub~ected to elevated temperatures. The
Michael adduct is formed very rapidly from the salt - i.e. the N-(dialkylamino-
alkyl)-2-methyl-~-alanine - and the latter is converted to N-(dialkylamino-
_ I _

alkyl~-methacrylamide at a temperature of from 140 to 230 C. Howe~er, this
process has the disadvantage that only N-substituted methacrylamides can be
produced from the corresponding methacrylic acid adducts and ~hat acrylic acid
amides cannot be produced by this route. The patent states that side reactions
predominate ~Jhen acrylic acid is used and that for the most part tar-like
materials result. Only small quantities of the desired N-substituted
acrylamides can be isolated.
Most surprisl~gly, it has now been found that N-(dialkylaminoalkyl)acryl-
amides of the general formula
'
CH2 = CH - C ~ Rl R3
\ NH-CH ~ C - CH N / (I)
R2 R~
wherein R1~ R2, R3 and R4 are in each instance straight or branched chain alkyl
groups having 1 - 4 carbon atoms, can be produced in good yields by reaction of
acryllc acid with tertiary aminoalkylamines of the formula
1~1 / 3 (II)
H2 2 1 2 \
R2 R4
wherein R1 to R4 are as stated above at temperatures of from 120 to 300 C.
(preferably 150 - 230C). Preferably the water that results from this reaction
is distilled off and preferably the acrylic acid and amine are in equimolar
amounts~

373
The following tertiary aminoalkylamines of the general formula II are
especially suitable for the invention:
3-dimethylamino-2,2-dimethylpropylamine
3-diethylamino-2~2-dimethylpropylamine
3-diethylamino-2,2-diethylpropylamine
3-dimethylamino-2,2-diethylpropylamine
Of these, 3-dimethylamino-2,2-dimethylpropylamine is preferred.
Completion of the reaction is very simple. The acrylic acid is added drop
by drop to the N,N-dialkylalkylene diamine, which optionally contains a
polymerisation inhibitor and, also optionally, a catalyst. When this is done,
the temperature can rise above 100 C. Once addition has been terminated, the
mixture is heated to a temperature of from 150 to 230 C., whereupon the
theoretical quantity of water i5 distilled off over a period of 1 to 5 hours.
The acrylamide that is formed is isolated by means of vacuum distillation. A
good yield of N-(tert-aminoalkyl~acrylamides results, and these can be used for
homo- and copolymerization without further processingO
Although it is not essential, it has been found advantageous to add
catalytic quantities of alkaline or acidic substances in a quantity of
approximately 0.5 - 2% wt., related to the total weight of the reactants.
These can be either non organic (such as hydrochloric acid, phosphoric acid,
calcium carbonate, or potassium hydroxide~ or organic (for example, acetic
acid, sodium acetate, or alcoholates)O In the same way, Iewis acids and bases
or ion exchange agents can be used. PhoRphoric acid and borium trifluoride are
preferred.
The reactions can be carried out in the presence of conventional
polymerization inhibitors - such as, for example, p-dioxyben~ol, p-methoxy~
phenol, copper powder, or copper salts. Aromatic amines - such as, for
example, N-phenyl-~-naphthylamine, N,N'-diphenyl-p-phylenediamine or phenothi-

azine - are preferred.
The inventin will now be described with reference to the foregoing
Examples 9 ~lich are for purposes of illustration only:
Example 1
A 500-ml three-neck flask fitted with a magnetic agitator, a thermometer,
and a short column with a distillation set was charged with 260 g ~2 mol)
3-dimethylamino-2,2-dimethylpropylamine; 4 g N-phenyl-p-nayhthylamine; and 4 ml
85% phosphoric acid. 144 g (2 mol) acrylic acid was added drop by drop for
0.5 hours, whereupon the temperature of the mixture rose to 150 C. Finally,
the mixture was heated to 200 C. in a nitrogen atmosphere for 2 hours, and
then stirred at this temperature for 1 hour. During this time, 35.5 g of the
distillate was obtained. Distillation was carried out in a vacuum after
cooling and 247 g (67%) N-(3-dimethylamino-2,2-dimethylpropyl)acrylamide9
boiling point 110-115 C. at 66.5 Pa, was obtained.
Example 2
Proceeding as in Example 1, 260 g 3-dimethylamino-2,2-dimethylpropylamine;
144 g acrylic acid; 4 g N,N'-diphenyl-p-phenylenediamine; and 10 ml
BF3-etherate were mixed. It was found possible to isolate 265 g (72%) of the
N-(3-dimethylamino-2,2-dimethylpropyl)acrylamide.
Example 3
Proceeding as in Example 1, 60 g 3-diethylamino-2,2-dimethylpropylamine;
27.3 g acrylic acid; 1.0 g N,N'-diphenyl-p-phenylenediamine; and 1 ml 85%
phosphoric acid were mixed. 47.5 g (59%) N-(3-diethylamino-2,2-dimethyl-
propyl)acrylamide, boiling point 139 to 141 C. at 1.33 Pa, were isolated.
Example 4
Proceeding as in Example 1, 173.5 g 3-dimethylamino--2-ethyl-2-butyl-
propylamine; 67 g acrylic acid; 2 g N,N'-diphenyl-p-phenylenediamine; and 2 g
calcium tert-butylate were mixed. 122 g (55%) N-(3-dimethylamino-2-ethyl-2-

butylpropyl)-acryla~ide, boillng point 129 C. at 66~5 Pa, was isolated.
Example 5
Proceeding as in E~ample l, 130 g 3-dimethylamino-2,2-dimethylpropylamine;
72 g acryllc acid; 3 g copper acetate; and 2 g 85% phosphoric acid were mixed.
130.5 g (71%) N-(3-dimethylamino-2,2-dimethylpropyl)acrylamide was isolated.
-- 5 --